It is known to provide a sanitary basin as a basin body or support of a foamed synthetic resin material, generally a polymer such as polystyrene, which can have a shape suitable for use of the body in a basin and a lining of a thermoplastic material which provides the water impermeability and esthetic appearance of the basin. Such basins can be used as shower pans, bath tubs, utility sink basins, sink basins for bathrooms, kitchens and other facilities. The term "basin" is used here in its broadest sense to refer to an upwardly open receptacle adapted to receive water for sanitary purposes.
In the past, the lining has been formed as a unit which can be loosely nested in the basin body or bonded therein with an adhesive. When the lining shell is only loosely nested in the basin body, the lack of a bond has proved to be a drawback which has affected the useful life of the basin in the frequently moist atmosphere in which a sanitary basin is used. Adhesive bonding is expensive. The adhesive often cannot be applied uniformly or homogeneously, and the moist atmosphere may affect the adhesive bond at least in part by water vapor penetration or diffusion into the adhesive.